Basics of Biology

Basic Chemistry For Biology

What are the major types of bonds?

Three major types of chemical bonds exist: covalent, ionic, and hydrogen. The form of bond that is established is determined by a specific arrangement between the electrons. Ionic bonds are formed when electrons are exchanged between two atoms and the resulting bond is relatively weak. For example, salt is held together by ionic bonds between sodium (Na) and chloride (Cl-) ions. Covalent bonds occur when electrons are shared between atoms; this form of bond is strongest and is found in both energy-rich molecules and molecules essential to life. For example, hydrogen and oxygen molecules in water are held together by covalent bonds. Hydrogen bonds are temporary, but they are important because they are crucial to the shape of a particular protein and have the ability to be rapidly formed and reformed, as in the case of muscle contraction. The following chart summarizes the three types of chemical bonds and their characteristics:

Type

Strength

Description

Examples

Covalent

Strong

Sharing of electrons results in each atom having a filled outermost shell of electrons

Bonds between hydrogen and oxygen in a molecule of water

Hydrogen

Weak

Bond between oppositely charged regions of molecules that have covalently bonded hydrogen atoms

Bonds between molecules of water

Ionic

Moderate

Bond between two oppositely charged atoms that were formed by the permanent transfer of one or more electrons